keyboardWillShow在eventFirstResponder之后没有立即调用通知

Question

我已实施keyboardWillShow:和keyboardWillHide:通知.我正在注册通知,直接触摸屏幕后它们工作正常UITextField,但是有问题.在viewDidLoad注册我正在通知的通知后,在我的右边becomeFirstResponder.键盘弹出,但keyboardWillShow:没有被调用(如上所述,只是第一次.从你调用函数注册通知的时间和实际注册的时间似乎有一个延迟,我不应该延迟执行becomeFirstResponder).有任何想法吗？

@objc func keyboardWillShow(_ notification: NSNotification) {
    print("Show")
    if let keyboardSize = (notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue {
        var userInfo = notification.userInfo!
        var keyboardFrame:CGRect = (userInfo[UIKeyboardFrameBeginUserInfoKey] as! NSValue).cgRectValue
        keyboardFrame = self.view.convert(keyboardFrame, from: nil)
        var contentInset: UIEdgeInsets = self.tv_main.contentInset
        contentInset.bottom = keyboardSize.height
        self.tv_main.contentInset = contentInset
        let indexpath = IndexPath(row: 0, section: 0)
        self.tv_main.scrollToRow(at: indexpath, at: UITableViewScrollPosition.top, animated: true)
    }
}

@objc func keyboardWillHide(_ notification: NSNotification) {
    print("Hide")
    if let _ = (notification.userInfo?[UIKeyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        let contentInset:UIEdgeInsets = UIEdgeInsets.zero
        self.tv_main.contentInset = contentInset

    }
}

override func viewDidLoad() {
    super.viewDidLoad()
    tv_main.delegate = self
    tv_main.dataSource = self
    tf_search.delegate = self
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillShow), name: NSNotification.Name.UIKeyboardWillShow, object: nil)
    NotificationCenter.default.addObserver(self, selector: #selector(self.keyboardWillHide), name: NSNotification.Name.UIKeyboardWillHide, object: nil)
    self.tf_search.becomeFirstResponder()
    if let placeholder = tf_search.placeholder {
        tf_search.attributedPlaceholder = NSAttributedString(string:placeholder, attributes: [NSAttributedStringKey.foregroundColor: UIColor.white])
    }
}

Answer 1

你应该叫becomeFirstResponder中viewWillAppear或viewDidAppear.